The present invention relates to a lock and, more particularly, to a lock providing improved security and resistance to attack.
The primary function of a lock is to deter individuals seeking unauthorized access to property. A lock typically comprises a core, sometimes referred to as a cylinder or a plug, which is selectively rotatable in the lock's body or casing to releasably secure a bolt or shank to the body of the lock. Typically, one or more locking pin(s), movable in the core, are arranged to selectively engage the body and prevent the core from turning in the body unless a correctly coded input moves the locking pin(s) to a position enabling rotation of the core. In a pin tumbler lock, for example, the locking pins comprise tumbler stacks which extend across the shear line separating the rotatable core from the body. When a correctly bitted key is inserted into the keyway, the tumbler stacks are moved to positions where the separation between the top and bottom tumblers of the stacks are all aligned with the shear line enabling rotation of the core and release of the bolt. Pin tumbler locks may be attacked by “picking,” mechanically manipulating the tumblers to their unlocked positions, permitting the lock to be operated without access to the correct key.
The correctly coded input for an electronic lock is typically a sequence of electrical signals transferred between the lock and a key. The sequence of signals is typically interpreted by a logic unit of the lock, or logic units of the lock and the key, and if the sequence matches a correct sequence, an actuator is energized to release the bolt or shank from the body.
While electronic locks are not subject to attack by manual tumbler picking, they are subject to attack by other methods that are also used to attack mechanical locks. Manually operated locks, including electronic locks, typically comprise a keyway into which a key is inserted. If the key includes the correct code, the core is released and the user can rotate the unlocked core by applying torque to the key. A lock may be attacked by inserting an object into the keyway and applying torque to the keyway in an attempt to overload and fail the locking mechanism. Another method of attacking a lock is to drill into the face of the core to destroy the components of the locking mechanism and free the core to rotate and release the bolt. What is desired, therefore, is a lock that is resistant to attack by drilling into the core or by applying excessive torque to the keyway.